Ch 2 · Permutations and Combinations

🧮 Formula sheet

1. 1.nPr = n! / (n−r)!
2. 2.nCr = n! / [r!(n−r)!]
3. 3.nCr = nC(n−r)
4. 4.nC0 + nC1 + ... + nCn = 2ⁿ
5. 5.Circular arrangement (clockwise = anticlockwise): (n−1)!/2